Datasheet

SLDU010
TI CONFIDENTIAL – NDA Restrictions
Page 13 of 50
Figure 7. DAC8574 and OPA2335 Buffers
3.1.3 Input Filters
Both the buffered DAC outputs and the Resistive Bridge outputs feed through the input filter on
the EVM before they connect to the inputs to the PGA400-Q1. The input filter is comprised of a
common-mode and differential filter made from ferrite beads and capacitors. When the EVM is
delivered to the customer, the ferrite beads L1-L4 are populated with 49Ohm resistors so that
the filters work as simple RC low-pass filters. If desired, the resistors can be replaced with
ferrite beads that meet the requirements of the final customer system. Similarly, the EVM comes
with an unpopulated footprint for an X2Y capacitor to replace the two common-mode and single
differential cap. To use the X2Y, uninstall the three populated filter caps on the desired
channels and install a single X2Y capacitor. The figure below shows the input filters on the
EVM.
Figure 8. Input Filtering on the PGA400-Q1 EVM